The present invention relates to medical devices in general, and in particular to radio frequency atherectomy devices for removing intravascular occlusions.
One of the most common types of vascular disease is characterized by reduced blood flow due to the presence of partial or total occlusions in a vessel. Such occlusions can contribute to the incidence of hypertension, cardiac arrest or stroke. To restore blood flow in an occluded vessel, it has become a routine procedure to bypass the occlusion with a healthy vessel obtained from elsewhere in the body. While bypass techniques are often successful, the procedure is fairly traumatic because the surgeon must access the blocked vessel externally in order to install the bypass.
One example of a less invasive technique used to restore blood flow requires the advancement of an atherectomy device including a cutting or grinding mechanism through the patient""s vasculature to the point of the occlusion. The cutting or grinding mechanism is then rotated at high speed to remove the occlusion from inside the vessel. While less traumatic than bypass surgery, the technique can be limited to the treatment of vessels through which the physician can route the atherectomy device. In addition, the cutting mechanisms are typically not very aggressive, thereby increasing the amount of time required to perform the procedure.
One technique that may offer some advantages over traditional mechanical atherectomy devices is to use RF electrical energy to remove an occlusion. The advantage of using RF electrical ablation energy is that the electrode can be made sufficiently flexible such that it can be routed through virtually any vessel. In addition, each RF pulse removes a greater amount of occluding material, thereby reducing the time required to complete the procedure.
As with any intravascular procedure, precautions must be taken to minimize the likelihood that RF electrical energy will perforate a vessel wall. Therefore, there is a need for an RF ablation system that minimizes the likelihood of vessel perforation while maintaining the advantages of RF ablation.
A radio frequency (RF) ablation system includes a catheter through which an RF electrode is routed to the point of a vascular deposit or occlusion. The system has a mechanism for pushing a vessel wall away from an area near the RF electrode that delivers an RF pulse.
In one embodiment of the invention, the catheter includes a number of tissue expanding jaws that can be engaged with the vessel wall and biased radially outward in order to move a vessel wall away from the RF electrode.
In another embodiment of the invention, the RF electrode includes a coiled portion at its distal end. The coiled portion has a radius that is larger than a radius of the catheter that delivers the electrode. The coiled portion of the electrode engages the vessel wall and moves it away from the area of the electrode that delivers an RF pulse.
In yet another embodiment of the invention, the RF electrode has a ring that surrounds a center portion of the electrode. The ring has a radius that is larger than the radius of the catheter through which the RF electrode is routed. The ring engages the vessel wall and moves it away from an area of the center portion of the electrode that delivers an RF pulse.